Please enable JavaScript.
Coggle requires JavaScript to display documents.
SEX DIFFERENCES IN BEHAVIOUR - Coggle Diagram
SEX DIFFERENCES IN BEHAVIOUR
SEXUAL DIFFERENTIATION - the developmental process of becoming a male or female
primary steps occur at fertilisation when chromosomes make up is determined (sex determination)
sex differentiation is complicated and potential for atypical development is high
sex differences in: chromosomal sex> gonadal sex (ovaries and testes) > morphological sex (body type)> hormonal sex (steroid hormone concentrations)> behavioural sex differences
Chromosonal:
pattern XYY = male, tall, learning difficulties (1/1000 male births)
pattern XXX = female tall learning difficulties (1/1000 female births)
pattern XXY = male infertile (1/1000 male births)
pattern X0 = female shoer infertile skeletal and organ abnormalities (1/3500 female births)
Gonadal:
at 6-7 weeks of development, thickened ridge of tissue on protokidney (germinal ridge) starts to develop into gonads
the default development is in a female direction > germinal ridge becomes an ovary
if the sex-determining region on the Y chromosome (Berta et al 1990) located on the Y chromosome activates and starts producing testis determining factors( a protein) (TDF)then testes form and development continues in male direction
if SRY is transported onto a X crhomosone, XX individuals will develop testes and male gwentials (46, XX testicular disorder of sex development, 1/20,000 births)
mutation of SRY gene, Swyer Syndrome: XY streak gonads, development of female genitalia
Morphological:
mullein duct system is the camel accessory sex organ: develops into Fallopian tubes, uterus and cervix
wolffian duct systems is the male accessory organ: develops into vas deferens, seminal vesicle
until 6 weeks old, embryos have both mullein and wolffian systems
androgens: hormones including testosterone, androstenedione, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA) and DHEA sulphate.
males show 3 peaks in androgen production:
10-18 weeks gestation (differentiation of reproductive system)
2-6 months after birth
puberty (secondary sexual characteristic)
what does testosterone do? - male sexual characteristics, libido, bine formation, metabolism, red blood cell formation, mood, confidence, memory fucntion
TESTOSTERONE SYNTHESIS IN MALES: leydig cell in the testes produce 95% in the male body from cholesteorol, remaining 5% produced by adrenal glands
TESTOSTERONE SYNTHESIS IN FEMALES testosterone is produced by the ovaries and varies across a women's menstrual cycle, 50% from ovaries and 50% from adrenal glands. adult female testosterone is approx 1/10th of males test levels. the enzyme aromatase converts testosterone into estradiol (aromatisation), the primary hormone responsible for female characteristics and sexual fucntioning
female sex hormones: - oestrogen's control the development and maintenance of female sexual characteristics, they are involved in cholesterol regulation, bone heart and skin health and mood,
ESTRONE (E1): only type of estrogen found in women after menopause, small amounts are present in most tissues, mainly fat and muscle
ESTRADIOL (E2): a steroid produced from testosterone by gonads
ESTRIOL (E3): a waste product, significant amounts are made during pregnancy
progesterone linked to menstural cycle, pregnancy and development of embryo, involved in bone, hair and metabolism and mood
all produced by ovaries, adnreal glands and placenta
estradiol and progesterone in males: men produce oestrogen's and progesterone from cholesterol in the testes, bones and adipose tissue. these are thought to act locally which limits their systemic effects - both make and females foetuses experience prenatal androgen exposure from secondary sources
control of sex hormones:
female mammals display cyclic gonadal function, males have constant reproductive fucntion.
gonadrotopin releasing hormone secreted from the hypothalamus determines pattern of release of gonadtropins 9hormones that act on the gonads) from the anterior pituitary gland.
the gonadotropins luteinising hormone and follicle stimulating hormone (FSH) stimulate both tested and ovaries
hormones and sexually dimporphic behaviours: - often animal models are used to understand effects of hormones on behavioural differences
simple behaviours only expressed by one sex
behavioural differences come from sex differences in the brain
sex differences in behaviour: adult rat mating behaviours e.g.lordis opposition in females vs mounting in males - castrationof male rats stops mounting behaviour, testosterone replacement therapy restores mounting behaviour (Davidson 1966). suggests mounting behaviour is controlled by circulating testosterone levels
behavioural sex differences: androgen/ oestrogen exposure during adulthood then activates the previously programmed male/ female behaviour patterns. - behavioural sex differences come from the brain - how is the brain demasulised or defeminised
why are females not masulised: estrogen production of foetuses/ newborn rats is low
rat fetuses produce alpha-fetoprotein, which binds circulating estrogen and removes it via the placenta and maternal liver
alpha-fetoprotein protects the foetus from estrogenic effects.
alpha-fetoprotein does not bind to androgens, so testosterone from male fetuses reaaches their brain where it is aromatised to estrogen and then has masculising effects
other sources of behavioural sex differences: the intra-uterine environment - uterine blood flow in rats from cervix to ovary: females 'downstream' of a male are more vulnerable to masculisinf effects (Ward 1981)
2-M females showed enhanced aggression, lengthened reproductive cycles and reduced attractively compared to 0-M females
stressed pregnant rats, male fetuses produce less androgen, adversely affecting their mating behaviours, increasing prenatal behaviours and decreasing rough and tumble play. stress hormones from the mother interfere with androgen production in the fetus
plastics and chemical agents such as pesticides may mimic oestrogen's and bind to estrogen receptors e.g. perinatal exposure to BPA can masculinise the brains of female rats, in 2011 the European Commission banned BPA from baby bottles.
exposure rot endocrine disrupting chemical can advance puberty and alter reporoductive functions in rodents